The D₁ agonists SKF 82958 and SKF 77434 are self-administered by rats

The reported failure of the prototypical (but partial) D₁ agonist SKF 38393 to support self-administration behavior contradicts hypotheses of D₁-mediated reinforcement. Here we demonstrate that rats will readily self-administer two SKF 38393 analogs, the partial D₁ agonist SKF 77434 and the full D₁ agonist SKF 82958; both compounds produce inverted U-shaped dose-response curves. When compared to the parent compound, both analogs display enhanced lipophilicity and somewhat decreased D₁/D₂ selectivity. It is suggested that these properties, rather than partial D₁ agonist efficacy, explain the failure of SKF 38393 to act as a reinforcer.